A plurality of virtual machines are executed on a host computer, the host computer including graphics hardware, and a display. The virtual machines write display data to their respective virtual desktop buffers. A virtual machine is selected to output to the display of the host computer. A composition buffer on the graphics hardware is enabled with respect to the selected virtual machine. The contents of the virtual desktop buffer associated with the selected virtual machine are copied to the composition buffer by the graphics hardware. The contents of the composition buffer are rendered and displayed by the graphics hardware. In addition, read access to the compositing buffer is restricted to the graphics hardware, thus preventing malicious software applications from capturing the display data across partitions.